The invention relates to a method and apparatus for measuring by capacitive means the tobacco density of the ends of rod-shaped articles which constitute or form parts of smokers' roducts, such as regular cigarettes, filter cigarettes, cigars, cigarillos, and the like. More particularly, the invention relates to that type of method and apparatus wherein a defect signal is generated if the measured tobacco density deviates from a preselected standard.
The invention furthermore relates to an arrangement for testing the tobacco density in the ends of rod-shaped articles, particularly cigarettes or other smokers' products or components thereof, using a capacitive measuring arrangement and a comparator device operative for generating a defect signal if the measurement indicates a deviation from a preselected tobacco density.
With known capacitive methods for determining the tobacco density in the ends of cigarettes, the measurement signals produced as a result of the testing are dependent not only upon tobacco mass but also upon tobacco moisture. It is true that the tobacco moisture variatons encountered during the manufacture of cigarettes are not very great; however, over long stretches of time they can lead to inaccuracy of the tobacco mass indication. For exmample, a cigarette end containing too little tobacco may not be recognized as being defective if the tobacco moisture is high; likewise, a cigarette end containing a proper amount of tobacco may be mistakenly recognized as being defective if the tobacco moisture level is particularly low.